I would start with Bond, CGP books at the right age for your dd, then work up to the ones for older ages. You need to make sure she has the basics, and teach her anything that school hasn’t (there will be chunks of the Y6 maths curriculum that she will need to know in the first term of Y6, for example, so you will need to teach those). If she isn’t currently reading widely and beyond her age, you will need to encourage her to do that, too.
Once you’ve covered the content, you can work on speed, accuracy and exam technique. Depending which schools you’re looking at, you may need VR, NVR and / or maths and english comprehension. The 11 plus forum is good for working that out, or the schools’ websites. If a computer-based VR/NVR is involved, there are some online test sites which you can use to simulate the test experience and get lots of practice. You can also sign up for mock exams, which are good both for the experience of being in a big hall with other kids, and because they will show you where your dd’s results are in the cohort (which you won’t know in a state primary).
It’s only once you’ve done all that, that the past papers come in handy. You don’t want to use them too soon, as each school usually only has a couple on their website. I would download the ones that are available now on the websites of the schools you’re interested in, as they may put up a different one by next year, so that way you’ll have more.